Of all the factors dragging down Republicans’ odds of success in the coming midterms, inflation seems to be the most important. According to the Real Clear Politics aggregation of polling results, 70.1% of Americans disapprove of President Donald Trump’s handling of inflation, and just 27.3% approve. Inflation also consistently ranks as one of the top two or three issues on voters’ minds.

Look at a chart of inflation in the US over the past few years, and this all seems a little odd. At 3.7% year-over-year as of September, inflation is definitely up since Trump returned to office in January 2025, but not by a huge amount. So-called core inflation, which excludes volatile food and energy prices to give a better read on underlying trends, is actually down. Food and energy prices are, of course, very important in Americans’ daily lives, so it’s understandable that the core-inflation drop doesn’t carry much political weight. But Trump’s approval ratings on inflation appear to be about the same as or slightly worse than President Joe Biden’s in mid-2022, when inflation was much, much worse, briefly topping 9%.

That Americans are gloomier about the economy than most economic indicators say they should be has been a recurring theme this fall. But one explanation for the extreme dissatisfaction with Trump on inflation may simply be that his actions have obviously made it worse, whereas it was less clear how culpable Biden was for the much bigger inflation wave during his tenure.

What causes inflation is not an entirely settled question. Economist Milton Friedman famously said in 1970 that “inflation is always and everywhere a monetary phenomenon,” meaning that in this post-gold-standard era, it’s mostly the purview of central banks. But what he meant was persistent inflation, not a temporary yet significant episode like that of 2021-2022. In retrospect, the Federal Reserve was probably too slow in reacting to the price increases of 2021, but it did raise interest rates pretty forcefully after that. It was also led throughout this period by a man appointed by Trump in 2018 and reappointed by Biden in 2022, so it’s a little hard to sort out partisan culpability.

The fiscal stimulus of 2020 and 2021, which was unprecedented outside of wartime, is another likely inflation culprit that was bipartisan in nature. Most of the stimulus was enacted while Trump was president, but some prominent economists warned at the time that the $1.9 trillion American Rescue Plan pushed through Congress by newly elected Biden in March 2021 — with the economy already growing rapidly — was overkill.

The fact that inflation rose faster in the US than in other developed economies in 2021 seemed to back this up. By 2022, though, the rest of the world had caught up.

Russia’s invasion of Ukraine in February 2022, which sent European energy prices skyrocketing but was less of an issue for the energy-rich US, was one reason inflation persisted longer in Europe than here. Overall, the picture is of a global inflation wave that the US participated in and contributed to, not a uniquely American phenomenon. Subsequent research on the 2021-2022 inflation increase has emphasized the huge global shifts in behavior during and after the Covid-19 pandemic that led to supply-chain bottlenecks and sharp price increases.

A new data series that has helped inform this discussion is Federal Reserve Bank of San Francisco economist Adam Shapiro’s “supply- and demand-driven PCE inflation,” which breaks down price changes in US Bureau of Economic Analysis personal consumption expenditures data by whether they’re accompanied by spending increases (demand driven) or decreases (supply driven). If either the price or spending changes are statistically indistinguishable from values predicted based on long-run trends, the price changes are classified as ambiguous in origin.

In this view, the inflation wave of 2021-2022 was primarily about supply constraints, although demand drove a lot of price increases, too. The modest uptick in inflation in 2025 was also somewhat more of a supply story than a demand one, probably attributable mainly to Trump’s tariffs. This year’s bigger increase is driven mostly by what Shapiro’s system classifies as ambiguous causes, but the cause doesn’t seem that ambiguous if you’ve been paying attention to current events.

Gasoline and diesel prices are up because Trump chose to attack Iran, and in response Iran chose to try to cut off marine traffic through the Strait of Hormuz, with the diesel price increase beginning to filter into the prices of other goods because it’s so central to transporting them. Americans have reduced energy consumption only slightly, though, as growth has held up and unemployment stayed low, thanks in part to a data-center investment boom that is propping up demand.

Or something like that — there are always multiple hard-to-disentangle forces at work in the gigantic US economy, and presidents usually get more credit and blame for economic outcomes than they truly deserve. But the indisputable link between the Iran war and fuel prices, and Trump’s failure to persuade anyone but his most die-hard supporters that the war was a good idea (even his vice president and eldest son have expressed doubts), means it’s entirely reasonable to blame him.

The repeated attempts by the president and other Republicans to shift the blame back to Biden, who did in fact preside over a big increase in prices that was probably partly his fault but left office with inflation clearly on the wane, if anything leaves them looking even more blameworthy.

Other factors at work here include big increases in health care costs for several million Americans caused by decisions by the Trump administration and Republican Congress; rising financial insecurity for a number of reasons that in some cases predate Trump; and possibly the unrealistic belief that ending inflation as Trump promised on the 2024 campaign trail would entail rolling back prices to pre-pandemic levels. But I wonder if the simplest answer isn’t the best — Trump is being blamed for inflation because it’s his fault that it has been rising.